I have ridden all the rides at US/IOA and do have to sit in the larger seats for Hulk and Dueling Dragons. I could not ride on Doctor Doom's Fearfall as they do not have modified seats. I agree that it truly does depend on how you carry your weight. I'm busty and tend to carry weight in my stomach. I was able to ride everything else without any issue. Including ROTM (just a lap bar, no shoulder harness/buckle), Jimmy Neutron, Simpsons, MIB, E.T., even WW Nuthouse Coaster at US. No issues at IOA for Spidey, Jurassic Park, Ripsaw, Bluto's Barges.